决定钎料钎缝强度的主要因素是（）。
A.钎料成分
B.钎剂
C.助焊剂
参考答案：A
Tom's first job was at a local restaurant in his early twenties，________he worked for seven years.
A．where
B．when
C．which
D．that
强迫油循环变压器停了油泵为什么不准继续运行？
